Upgrading or changing memcahe client without invalidating the memcache.

[memcached-user]

Hello.

 We wanted to change the hashing strategy of the memcache (memcache.hash_strategy) from "standard" to 
"consistent". Is there a easier way to do this without invalidating all of the memcache?

If we do change it on the run, All the key will be a miss and the load on db will increase. 

 

[Matt Ingenthron]

No, you'll likely have a large set of misses when you make the change.
Best to find a time when the workload is as low as possible.

Good luck,

Matt

[memcacheduser]

We have come up with a Not so elegant solution. 

1. Install php-memcached, Now you have 2 clients side by side. 

2. Write with both the client, php-memcache(cA) and php-memcached(cB), cB will have a certain prefix. Read from cA.

3. After cache is warmed up.  start reading from cB. 

4. upgrade/change hash to cA. 

5. Let the cache warm up.

6. Start reading from cA. 

7. retire cB. 

But this would guarantee that the memcache is always available.